Routing switchers may also be called signal selectors, audio/video (AV) selectors or simply routers. A standard routing switcher may have multiple video and audio signals from a number of sources, such as Videotape Recorders, Media Servers, Satellite Receivers, etc. connected to the routers inputs. The router's output or outputs can go to one or more destinations, such as Videotape Recorders, Video/Audio Mixers, Video/Audio Monitors, etc. Which input connects to which output(s) may be selected by a user with the push of a button, without disconnecting/reconnecting audio and video cables.
In a television facility, a single program may require switching to a plurality of different channels or stations. In some situations, the audio that is embedded may not be appropriate for each channel. For example, a different language may be needed or a dubbed version of the audio track may be required. In these situations, the audio output must be switched independently from the video. A routing switcher may be employed to perform this task.
When constructing a signal switching infrastructure for a television facility, a choice needs to be made to use video with embedded audio as a single switching level or to use independent audio routing matrices to switch audio separately from video. The advantages of switching video with embedded audio include a substantial reduction of switching hardware and system cabling when compared with separate audio switching matrices. Many modern devices such as video tape recorders, media servers and master control switchers support video inputs and outputs with embedded audio.
A principal disadvantage is that conventional serial digital video switching matrices do not permit independent switching of the embedded audio streams within the video signal. This makes it difficult to combine, e.g., the video from input #1 with the audio from input #2 at an output of the switching matrix. In many facilities, especially production/post production, or where multi-channel and/or multilingual audio must be considered, this limitation has dictated the use of a separate audio switching infrastructure.
In the past, separate audio switching infrastructures have been employed (with the attendant increase in cost, space needed, cabling and power consumption). Hybrid systems using outboard audio embedding and de-embedding devices in conjunction with serial digital video switching matrices have also been employed. This alternative is also costly and complex to implement.